thermostats, thermoscopes ...
DICTIONARY: Thermometer: An instrument for determining temperature
consisting typically of a glass bulb attached to a fine tube of glass with a
numbered scale and containing a liquid (as mercury or colored alcohol) that is
sealed in and rises and falls with changes of temperature.
Thermometer: An instrument that measures the temperature of a system in a
quantitative way. How hot is the
oven? How cold is it outside?
DEVICE: Thermostat: A thermometer that uses its temperature measurements *to
control* other equipment. Set the
oven to maintain 350 degrees. I want the air conditioner to keep the house at 72 degrees.
This is NOT the topic of discussion - it is simply offered for
of the earliest devices used to measure temperature (thermometers) were called
thermoscopes. They were simple
devices consisting of a glass bulb with a long tube extending downward into a
container of coblored water that was open to the atmosphere.
Galileo,in 1610, is rumored to have used wine - good choice!
As the air in the bulb was heated or cooled, the level of the liquid in
the tube would rise or fall reflecting the change in the air temperature. By
marking the side of the tube, a quantitative guide to temperatures was achieved.
came the "spirit" thermometers. In
1641, the first use of a sealed alcohol-in-glass device, with (temperature)
marks on its stem was the beginning for our modern thermometer.
This method was developed for Ferdinand II, Grand Duke of Tuscany.
you aware that Anders Celsius (1701-1744) - you know ...Celsius - actually used
the reverse scale (as we know it today) where100 represented the freezing point
and zero the boiling point of water?
year after his death, in 1745, Carolus Linnaeus of Upsula, Sweden, turned things
on their heads. He designed a scale
in which the freezing point of water was zero, and the boiling point 100.
the mathematicians: To convert from Celsius to Fahrenheit:
Multiply by 1.8 and add 32. ° F = 1.8° C + 32
early bulb thermometers relied upon the principal that liquids change volume
relative to temperature. These
liquids, water, alcohol, mercury rise and fall when subjected to heat and cold. In
order to gain a better handle on temperatures, along came the bimetallic strip
thermometer. The use of metal
rather than liquids has proven to be a much better gauge of measuring actual
bimetal thermometer uses the relationship of different types of metals expanding
at different rates as they warm and cool. These
metals are most often copper and iron. (Copper
has the greater expansion coefficient and thus will expand more when heated and
contract more when cooled.) These
two different metals are bonded together in sandwich like fashion and can
withstand fairly high temperatures. Consequently, these are often found in
to Begin Cooking
brings us now to our trusty barbecue pit. Each
pit should be equipped with a reliable, sturdy and accurate bimetal thermometer,
(also referred to as a chamber thermometer).
This device measures the internal temperature within the cooking chamber
- preferably at the vertical location where you place the meat.
cooking, say at 210 to 225 degrees (the preferred temperature range for
barbecuing) you are planning for a much longer cooking period than if you are
cooking at say 350 degrees (which is roasting). Meat cooking at 210 degrees obviously cooks the meat much
slower than the higher temperatures. At
these lower temperatures the result are meats that are more tender than if
cooked at higher temperatures. If you are using an *inaccurate* thermometer, you may be
cooking for long periods of time at temperatures in excess of 260-270 degrees or
possibly even less than 200 degrees.
would be remiss in not commenting on many of the factory installed thermometers
offered on barbecue pits. First of
all, if you have a thermometer on your pit that says WARM, MEDIUM, HOT, then you
are literally "shooting in the dark" on the actual temperature.
They are simply inaccurate at best.
You have as good (if not better) chance of determining the temperature by
placing your hand on the side of the pit as looking at that type of gauge. Second,
one person's pit may read medium which may be another person's HOT or even WARM.Third,
manufacturers using this type of thermometer are offering theleast expensive
measuring device (not a thermometer!) to make their pits more affordable.
you want to control heat, you have to know the temperature at which you are
cooking. It is impossible to even
begin to estimate the time it will take to cook the meat without a thermometer.
let's now look at the ideal placement of the bimetal thermometer on your pit. We all know that heat rises.
Cooler air sinks. This is
true in your home and in your barbecue pit.
Using a typical pit
is approximately 2 feet in diameter (or, if it is rectangle, 2 feet from top to
bottom) it is not uncommon to have anywhere from 40 to 70 degrees difference
from the surface of the cooking grate to the top of the cooking chamber.
Many manufacturers place their thermometers in the lid or on top of the
cooking chamber. Nope,
that's not the correct place to measure the cooking temperature. Place your thermometer at or very near the locationwhere the
meat is being cooked. If placed too
high, you will be measuring a much higher temperature and actually be cooking
the meat up to 50 degrees cooler!
If you already have a bimetal chamber thermometer (or you have just bought a new one), we recommend testing it once a year. These guys are exposed to extreme temperatures and weather and sometimes will corrode or become inaccurate. An inaccurate thermometer is worthless.
test your thermometer, simply remove the thermometer from thebarbecue pit and
carefully place the stem of the thermometer into boiling water. It should read at, or very near, 212 degrees. Assuming this
is working properly, next place the stem in a glass of water with ice cubes.
Use the stem to stir the water and ice.
It should read 33 or 34 degrees. Using
a glass of alcohol and ice will make it closer to 32 degrees.
ONLY bet in controlling the cooking process on the outdoor barbecue pit is to
know your temperatures!
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